[postgis-devel] Does ST_Max_Distance work on anyone's install

Obe, Regina robe.dnd at cityofboston.gov
Wed Oct 29 10:51:41 PDT 2008


Ah okay I agree with Strk on that one. 

 For the example he gave I would expect
it to return 10 too since I think the common use case would be for example

Given a road a and road b -- what's the furthest that anyone would need to trek
(excluding routing obstacles)  from anywhere on road a to get to anywhere on road b.

Hmm I wonder how much effort it would be to fix it.  I guess strk gave up on it
so that would mean I am probably  too stupid to attempt it.  Pity though.

Well as functions go I guess its not the most important thing.  Would be more useful for polygons anyway since city to city commuting is more interesting.

-----Original Message-----
From: postgis-devel-bounces at postgis.refractions.net on behalf of Paul Ramsey
Sent: Wed 10/29/2008 12:23 PM
To: PostGIS Development Discussion
Subject: Re: [postgis-devel] Does ST_Max_Distance work on anyone's install
 
And there's the answer:

http://postgis.refractions.net/pipermail/postgis-devel/2004-August/000437.html

On Wed, Oct 29, 2008 at 9:21 AM, Paul Ramsey <pramsey at cleverelephant.ca> wrote:
> I'm pretty sure it existed and worked at one point, because Dave wrote
> it originally for a particular data processing use case Refractions
> had. Why strk turned it off is for him to say :)
>
> P.
>
> On Wed, Oct 29, 2008 at 4:17 AM, Mark Cave-Ayland
> <mark.cave-ayland at siriusit.co.uk> wrote:
>> Obe, Regina wrote:
>>>
>>> http://postgis.refractions.net/documentation/manual-svn/ST_Max_Distance.
>>> html
>>>
>>> I noticed Robert Burgholzer tried to use it and couldn't either
>>> evidentally.  Though I thought it worked once upon a time.
>>
>> Strange. There is actually code in the function to "do things"TM but the
>> elog() at the top of the function causes it to exit straightaway!
>>
>> Looking at svn log you can see the following comments:
>>
>> ------------------------------------------------------------------------
>> r756 | strk | 2004-08-26 17:55:09 +0100 (Thu, 26 Aug 2004) | 2 lines
>>
>> max_distance() raises an 'unimplemented yet' error.
>>
>> ------------------------------------------------------------------------
>>
>> ...
>>
>> ------------------------------------------------------------------------
>> r753 | strk | 2004-08-26 16:02:59 +0100 (Thu, 26 Aug 2004) | 2 lines
>>
>> Added (bogus) max_distance(geom,geom)
>>
>> ------------------------------------------------------------------------
>>
>>
>> And the relevant commit diff is:
>>
>> pg83 at zeno:~/src/postgis-svn/trunk/lwgeom$ svn diff -r 755:756
>> lwgeom_functions_basic.c
>> Index: lwgeom_functions_basic.c
>> ===================================================================
>> --- lwgeom_functions_basic.c    (revision 755)
>> +++ lwgeom_functions_basic.c    (revision 756)
>> @@ -1735,6 +1735,9 @@
>>        double maxdist = 0;
>>        int i;
>>
>> +       elog(ERROR, "This function is unimplemented yet");
>> +       PG_RETURN_NULL();
>> +
>>        geom1 = (LWGEOM *)PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
>>        line1 = lwline_deserialize(SERIALIZED_FORM(geom1));
>>        if ( line1 == NULL ) PG_RETURN_NULL(); // not a linestring
>>
>>
>> I'd say from this that strk had a go at implementing this function but
>> realised it didn't work properly and so disabled it soon afterwards :(
>>
>>
>> HTH,
>>
>> Mark.
>>
>> --
>> Mark Cave-Ayland
>> Sirius Corporation - The Open Source Experts
>> http://www.siriusit.co.uk
>> T: +44 870 608 0063
>> _______________________________________________
>> postgis-devel mailing list
>> postgis-devel at postgis.refractions.net
>> http://postgis.refractions.net/mailman/listinfo/postgis-devel
>>
>
_______________________________________________
postgis-devel mailing list
postgis-devel at postgis.refractions.net
http://postgis.refractions.net/mailman/listinfo/postgis-devel



-----------------------------------------
The substance of this message, including any attachments, may be
confidential, legally privileged and/or exempt from disclosure
pursuant to Massachusetts law. It is intended
solely for the addressee. If you received this in error, please
contact the sender and delete the material from any computer.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-devel/attachments/20081029/cd44aea6/attachment.html>


More information about the postgis-devel mailing list